The environment of the present invention presents a trailer hitched to an automobile which must be moved to a position in a parking or storing area inaccessible to the automobile. Many times in order to move the few feet necessary to finally position the trailer, a great amount of effort is necessary and often requires two or more able-bodied persons to physically lift the trailer off the ball socket of the automobile and move the trailer to its final storage location.
Previously available devices for maneuvering trailers have not been entirely satisfactory. For example, the device disclosed in the U.S. Pat. No. 3,861,483 to Pavelka requires two side-by-side powered wheels plus two casters for stability, because the ball connection to the ball socket type hitch of the trailer does not provide stability against tipping in either the fore and aft or the lateral direction. The two powered wheels require a costly differential gear to avoid excessive difficulty in turning which would otherwise result from tire scrubbing inherent in such an arrangement. Because the device connects to the hitch of the trailer, it cannot be connected until the trailer is disconnected from the towing hitch on the car.
The Kimball U.S. Pat. No. 3,439,764, employs a single driving wheel directly under the load, with no casters or auxiliary wheels to aid in distributing the load. Auxiliary wheels are used only when the device is detached from the trailer, and then are used to elevate the driving wheel off the ground. Because only a single wheel carries the trailer load, the socket which receives the tube of the trailer jack must be rigid for stability, making it more difficult to traverse uneven terrain. Another disadvantage is the placement of the socket over the drive wheel, a position which increase its height and may require the trailer tongue to be lifted off the towing hitch on the car in order to permit the device to roll in under the jack tube.
The U.S. Pat. Nos. to Holtzclaw et al (3,370,666), Jacobs (3,123,173), Bueckner (3,865,204), Hawgood (3,156,315), Peckham (3,356,172) and Shields et al (3,942,823) show other examples of trailer moving devices employing similar concepts with either two or more laterally spaced wheels or with the load of the trailer being directly over one of the wheels being driven. They present similar problems of stability, maneuverability, convenience and cost.